In Sickness, In Health

History Ties Disease And Health In Fateful Tangle

Their internal organs were almost instantly in a state of meltdown, transformed by an unseen killer.

The sickness stunned the world.

Yet at the height of the battle with the Ebola virus, an official for the World Health Organization summed up the crisis in a metaphor. His words illuminate the fine line between health and all disease.

''The history of human beings,'' WHO epidemiologist Andre Lubanov told reporters in Zaire, ''is the history of disease.''

We get sick. No doubt about it. Visible and invisible threats abound.

Some, such as Ebola, or the human immunodeficiency virus, seem to arrive by ambush, bursting onto the scene without notice; others, such as cancer, come on insidiously; and scores of others are tucked into the complicated messages of genes.

Medical anthropologists and biologists, the people who study why we get sick, say the conditions that have induced illness over the millennia have changed.

And the reasons why people get sick will continue to change, they say. If history is any guide, there is every reason to believe that what causes sickness in the late 20th century may not do so 200 years from now.

Smallpox, the viral infection that killed more people than any other disease known to humankind, is gone - eradicated in a decadelong vaccination program. The last documented case was in 1977.

The link between the vital need for vitamin C in the 19th century obliterated scurvy, a disease typified by anemia, spongy gums and bleeding from mucous membranes.

Vitamin D cured the soft-bone disease known as rickets.

Still, humans will never be free of sickness, scientists say, and exploring why that is so is producing new insights into the continuing struggle between health and disease.

For example, some conditions that used to keep us well now make us sick. And conditions that now threaten our lives were of little or no concern in earlier eras.

Cancer, for instance, was rare thousands of years ago because most people never lived long enough to develop it.

Heart disease rates shot up as societies became increasingly ''civilized,'' as did rates of Type 2 diabetes, the kind that usually occurs in midlife.

The hard work of farming gave way to the ''soft'' work of offices. Cigarettes, processed foods and listless hours in front of television sets all conspired against the heart. They also set the stage for Type 2 diabetes.

Infectious diseases, although a perennial threat, decreased dramatically with the advent of antibiotics about a half-century ago. Yet infectious diseases again are on the rise because scores of bacteria have found ways to repel the drugs.

''People are healthier today than they've been in history,'' said Dr. Kenneth Roux, professor of biology at Florida State University in Tallahassee. But it's a false sense of health, he said. ''The gene pool probably has never been weaker.''

He cites Type 1 diabetes, the kind that occurs in childhood and requires daily insulin injections, as a prime example.

''From a cold, hard perspective the gene pool is getting weakened because people are passing along genes that wouldn't have been transmitted in earlier generations,'' Roux said.

Prior to the development of insulin therapy earlier in this century, not many people with Type 1 diabetes lived long enough to have children and pass along the diabetes gene.

Medicine helped make a very rare condition a much more common one.

In other instances, medical science is at a loss to treat effectively genetic illnesses that are passed rapidly throughout populations. Ironically, some of the most devastating inherited diseases are caused by genes that may once have promoted health.

For example:

The gene that causes cystic fibrosis may have helped protect against cholera.

The gene that leads to sickle cell anemia may have provided protection against malaria.

The gene that leads to Tay-Sachs disease, a devastating, metabolic disorder that launches a lethal attack on the central nervous system, may have protected people from tuberculosis.

Dr. Sherif Gabriel, a cystic fibrosis researcher at the University of North Carolina in Chapel Hill, speculates that the manifestations of cystic fibrosis are extreme features of a gene that used to confer health.

Ancestors of modern Europeans evolved a way to survive cholera epidemics, Gabriel contends, because the gene confers the ability to retain salts and fluids.

The tiny, comma-shaped bacterium that causes cholera induces severe diarrhea and vomiting, forcing the infected person to lose vital electrolytes, such as chloride, sodium and potassium. With an electrolyte-preserving gene, those who carried it were hardier and able to ride out waves of cholera.

Trouble is, when people inherit two copies of the gene, disease is the result.